The present invention relates to a load lifting apparatus suitable for use in a materials-handling operation, which enables loads (particularly, heavy objects) of various shapes and structures to be readily clamped and allows the loads to be readily released at a desired position after they have been lifted and moved thereto.
To lift and move to a desired position a heavy load, e.g. a concrete block or pipe or a steel pipe, the following method has heretofore been employed: A wire rope or chain is wound around the load, and the other end of the wire rope or chain is engaged with a hook or the like of materials-handling equipment. In this state, the load is lifted and moved to the desired position, and then the wire rope or chain is removed from the load.
Some loads are lifted and moved to a desired position as follows: Engagement members, e.g. bolts or hooks, for engaging a wire rope or chain have previously been attached to the loads, or the loads have been arranged such that these engagement members can be attached thereto. In a materials-handling operation, a wire rope or chain is engaged with engagement members previously attached to a load or engagement members attached thereto at the site of work, and the other end of the wire rope or chain is engaged with a hook of materials-handling equipment. After the load has been lifted and moved to a desired position, the wire rope or chain is disengaged from the engagement members attached to the load.
Materials-handling equipment, e.g. a crane, has a lifting apparatus that has clamping members for clamping a load as an object to be lifted. The clamping members of the lifting apparatus are opened by human power or using a jig, e.g. a hydraulic device, to pick up a load to be lifted. Then, the load is lifted and moved to a desired position by the materials-handling equipment. At the destination, the clamping members are removed from the load by human power or using a jig, e.g. a hydraulic device.
The above-described conventional method in which a wire rope or chain is wound around a load or engaged with engagement members by a manual operation suffers from the problem that the materials-handling operation is difficult because it is carried out by a manual operation and, at the same time, it is dangerous at a shaky work site.
The conventional method in which the clamping members of materials-handling equipment are operated by human power or using a jig, e.g. a hydraulic device, suffers from the problem that it is difficult to operate the clamping members at a job site and, at the same time, the use of a hydraulic device or other similar jig involves a mechanical failure and causes the overall size of the equipment to increase.
If such a jig as a hydraulic device is mounted on a vehicle or the like, it occupies an installation space, resulting in a reduction of the space for loading an object to be lifted, and also causing the cost of the equipment to increase.